One year experience of MET gene exon 14 skipping analysis in lung cancer: Identification of 18 cases by NGS

e20055

Background: Lung adenocarcinoma (LAC) is the most common histological type of non-small-cell lung cancer and is one of the malignancies with the most evolved personalized treatments based on molecular characteristics of the tumor. Mutations in EGFR, HER2 and BRAF, specific translocations of ALK, ROS1, RET and amplification of MET all have standard diagnostic importance and lead to specific treatment options for the individual LAC patients. Recently, in 2-4% of LAC MET gene mutations leading to skipping of exon 14 were found. These mutations were described to occur more frequently in tumors with sarcomatoid histology. LAC with MET exon 14 skipping mutations showed impressive, although temporary, responses to MET tyrosine kinase inhibitors (TKI) crizotinib, cabozantinib and capmatinib. We will present our experience with routine molecular diagnostic detection of the most common MET exon 14 skipping mutations. Methods: In January 2016 we included in our standard, DNA based, molecular diagnostics custom-made NGS analyses 4 amplicons for detection of MET skipping mutations. The analyses were performed on microdissected FFPE tissue sections or routine histology or cytology stained preparations. Nine different mutations were validated for their effect on splicing by RT-PCR on RNA isolated from the same tissue samples. Results: Between January 2016 and January 2017 676 routine molecular diagnostic analyses on LAC were performed. In 18 (2.7%) cases MET mutations were detected possibly resulting in exon 14 skipping. Nine out of 16 different mutations were tested by RT-PCR and all 9 were demonstrated to result in MET exon 14 skipping. Conclusions: MET exon 14 skipping mutations can reliably be detected in routine pathology tissue samples. These analyses can easily be included in routine molecular diagnostic NGS. When necessary, confirmation of the mutational effect on RNA splicing can be implemented as well. Routine identification of MET skipping mutations (2.7% of cases) adds substantially to the personalized targeted treatment strategies for LAC patients.